Tunneling machine

ABSTRACT

A tunneling machine having a front portion on which two swinging frames with rotating cutter heads are mounted. Four parallelly arranged double-acting hydraulic advance jacks interconnect pivotably the front portion and a rear portion. Both the front portion and the rear portion can be immobilized in the tunnel by means of gripper jacks. The advance strokes of the four advance jacks can be pre-set individually so that these jacks steer the front portion relative to the immobilized rear portion simultaneously with advancing the front portion.

[ 51 Oct. 3, 1972 United States Patent Birrer [54] TUNNELING MACHINE Primary Examiner-Emest R. Purser Attorney-Munson & Fiddler [72] Inventor:

ABSTRACT Sweden A tunneling machine having a front portion on which [22] Flled' July 1970 two swinging frames with rotating cutter heads are [21] Appl. No.: 56,909 mounted. Four parallelly arranged double-acting hydraulic advance jacks interconnect pivotably the front portion and a rear portion. Both the front por- [52] US. CI.........................299/31, 61/45 D, 299/71 tion and the rear portion can be immobilized in the tunnel by means of gripper jacks. The advance strokes of the four advance jacks can be pre 51 int. .......................E0lg3/04 .299/31, 32; 61/45 D, 85

Field of Search...

-set individually References Cited so that these jacks steer the front portion relative to UNITED STATES PATENTS the immobilized rear portion simultaneously with advancing the front portion.

1,201,097 10/1916 Proctor........................299/3l 2,919,121 12/1959 Ruth............................299/3l FOREIGN PATENTS OR APPLICATIONS 8 Claims, 3 Drawing Figures 1,019,886 2/1966 Great Britain...............299/31 w 5 m 6 F 5 w 0 9 9 n N 4 5 2 5 4 3 "1% 4 w. 31 4 a 4 a EV @u E a t .4 a m :M la/J0 I I 5 a W m h I H ,V Wd 0 /h w l .u r l 9 3 n 2 2 3 4 n .J n 4 K 6 PATENTEDnm 3 I972 SHEET 1 OF 3 ii 2 GM bl in kixlilh \\I Q INVENTOR. J SQf 8 fr -er BY ammbm PATENTEDncI 3 m2 SHEET 2 OF 3 mm mi? Q Q F Av-W m 1mm I l h illlill IIIII'IA m m Wm B Q 3 mm bm INVENTOR. J 5%) B irra/ HY PATENTEDnma 1972 SHEET 3 BF 3 I N V E NTOR Y TUNNELING MACHINE This invention relates to tunneling machines which have a cutting device mounted on a front portion of a frame structure for power actuated swinging about a transverse axis.

It is an object of the invention to provide such a machine which has improved advancing and steering means.

The invention is described with reference to the accompanying drawings in which an embodiment of the invention is described by way of example.

In the figures:

FIG. 1 is a top view of a tunneling machine,

FIG. 2 is a side view of the machine illustrated in FIG. 1, and

FIG. 3 is a fragmentary diagram of the electrohydraulic system of the machine illustrated in FIGS. 1 and 2.

The tunneling machine illustrated in the figures has a frame structure which consists of a rigid front frame 11 and a rigid rear frame 12 which are interconnected by means of four parallelly arranged double acting power jacks 13-16, all of the same size. The power jacks 13-16 are universally pivotably connected to the frames 11, 12.

Two cutting devices in the forms of segment-shaped frames 17, 18 each having three cutter heads 19 are swingably mounted on pairs of pivots, 20, 21, on the front frame portion 11 and two pairs of hydraulic jacks, 22, 23, are arranged to effect the swinging. The pivots 20, 21 provide vertical swing axes for the swingable frames 17, 18. The cutter heads 19 are rotatable and have a number of detachable cutter bits 24 (illustrated only on FIG. 1) on their peripheral circular surfaces. The lowest cutter heads have also cutters 25 (FIG. 2) for smoothening the floor. For clarity, the upper cutter heads are removed in FIG. 1.

The cutter heads 19 are individually rotated by means of motors and gearings indicated at 26. The motors are preferably electric motors, but may also be hydraulic fluid motors.

The front frame 11 slides on the floor on a wide shoe 54 and it can be braced between the side walls of the tunnel by means of a pair of horizontal jacks 27, 28 which pivotally bear wall engaging shoes 29, 30. Alternatively or simultaneously the front frame can be braced between floor and roof by means of two pairs of jacks 31-34 which also pivotably bear shoes 35-38.

The rear frame portion 1 1 has two pairs of horizontal jacks 39, 40; 41, 42 by which it can be rigidly braced between the side walls of the tunnel. There are shoes 43-46 pivotably mounted on these jacks. The rear frame portion 11 has also two shoes 47, 48 sliding on the floor and two hydraulic jacks 49, 50 with roof engaging shores 51, 52 so that it can alternatively or simultaneously be braced between roof and floor. The shoes 51 52 are pivotably mounted.

On the lowest cutter head on each swingable frame 17, 18 there are mucking plates 53 which co-act with the wide shoe 54 so that the debris is being scraped on to a central band conveyor 55 when the frames 17, 18 swing inwardly. The conveyor 55 discharges into a transverse band conveyor 56 which in turn feeds another band conveyor 57 on a trailer 58. The trailer 58 is connected to the rear frame 12 by means of a pull rod 59 and it carries the operators seat, hydraulic pumps, a ventilation unit with a suction hose 60 and other accessories.

In FIG. 3, there are illustrated schematically the four advance jacks 13-16 and the hydraulic system for effecting controlled extension and retraction of these jacks. There are also illustrated electric circuits for actuating some valves in the hydraulic system. Hydraulic fluid lines are illustrated by full lines, but electric lines by broken lines. The reference numeral 65 refers to a pump and tank unit which supplies fluid to a branched main supply conduit 66. Each of the four advance cylinders 13-16 has two pressure chambers 67-74, each pair being connected to a control valve -78 by means of conduits 79-86. The control valves 75-78 are connected to the main supply conduit 66 by means of conduits 87-90 and connected to tank by means of a branched drain conduit 66a. In each of the supply conduits 87-90 there is a volume meter 91-94 connected. Hydraulic motors such as sliding vane motors, axial piston motors or hydraulic motors of any other suitable type may be used as meters. Each of the meters drives mechanically a counter-and-switch unit with a counter 99, 100, 101, 102, and a switch 103, 104, 105, 106. Each counter is arranged to shift its associated switch into off-position when the meter 91, 92, 93, 94 has rotated a predetermined number of revolutions. In the figure, schematically, there are illustrated arms of the counters actuating the switches. The counter-andswitch units are not illustrated in details since they are of a standard type. Each of the switches 103-106 is connected in a circuit arranged for actuating one of the valves 75-78. In the circuits there are included relays 107-110 in a usual way. A main relay 63 controlled by a conventional sequence unit is common to all the illustrated circuits.

The meters 93, 94 are mechanically connected by means of a clutch 111 which is operated by a jack 112. A solenoid valve 113 controls the jack 112. When the clutch 111 is in disengaged position, the meters 93, 94 are free to run individually, but when the clutch is engaged, the meters rotate conjointly so that equal and simultaneous strokes of the jacks 15, 16 are achieved even if one of these jacks has to overcome a larger re sistance than the other. In that case, the clutch-connected meters work as a booster group with one meter working as a motor driving the other which then works as a pump. The meters 91, 92 are connected in the same way by means of a clutch 114 operated by a jack 115 which is controlled by a solenoid valve 116.

The speed of extension of the advance jacks 13-16 is limited by means of one-way restrictors 117-120 which can be actuated to permit fast extension by means of hydraulic pressure in a control conduit 121 controlled by a solenoid valve 122. The electric circuits for actuating the valves 116, 122 are not illustrated.

The general operation of the machine will now be described. Assume that the swingable frames 17, 18 have been returned idle to the position shown in FIG. 1. The advance jacks 13-16 have retracted completely and they have pulled the rear frame 12 forward. During the advance of the rear frame 12, the jacks 27, 28 and/or 31-34 on the front frame 11 are actuated to brace the front frame in the tunnel, but the jacks 39-42, 49, 50 on the rear frame 12 slide along under reduced pressure to guide the rear frame or they may be retracted completely from engagement with the wall.

Now, the rear frame 12 is braced in the tunnel but the front frame 11 is released and the advance jacks 13-16 are actuated to advance the front frame 11 a distance 61. The cutter heads rotate and cut during this movement which therefore is called a feed cut. The front frame 11 is now immobilized in the tunnel by means of the jacks 27, 28 and/or 31-34, and the swinging of the swingable frames 17, 18 towards the center of the tunnel is initiated. The cutter bits 24 of each cutter head 19 now undercut the tunnel face, i.e. they cut a kerf as indicated by the line 62 in FIG. 1, and the ridge which is left at the back of the cutter bits is broken away by the tapered back surfaces of the cutter bits. This mode of operation is well known for instance from the Lauber U.S. Pat. No. 3,446,535 and Wohlmeyer U.S. Pat. No. 2,758,825. Since some overlapping is advantageous, the very last portions of the swinging movement of the swingable frames are not simultaneous but in sequence. The two swinging frames 17, 18 return idle back to their back swung positions (FIG. 1), the advance jacks 13, 16 advance the front frame another step, and another swinging movement swing cut of the swingable frames is effected. This sequence is repeated until the advance jacks l3 16 are fully or nearly fully extended. Then, the rear frame 12 is advanced by means of the advance cylinders as previously described so that the front frame can again advance in steps. The described sequenced operation is carried out automatically since the jacks 31-34 and/or 27, 28 for bracing the front frame 11 in the tunnel, the jacks 39-42 and/or 49, 50 for bracing the rear frame 12, as well as the jacks 13-16 for moving the two frames l1, l2 longitudinally relative to each other, as well as the jacks 22, 23 for swinging the frames 17, 18, are controlled by solenoid valves which in turn are controlled by means of the sequence unit.

The front frame 11 is guided by its horizontal jacks 27, 28 during its advance. To this end, one of the jacks 27, 28 can preferably be locked hydraulically and the other actuated with reduced power so as to permit sliding of the shoes 29, 30 on the side walls of the tunnel. However, the valves for effecting this are not illustrated in the drawings. Both jacks 27, 28 may instead be locked hydraulically during advance since the width of the tunnel will be very constant.

The operation and control of one of the advance jacks the jack l6 will now be described. It is to be understood that the other three advance jacks are controlled and actuated simultaneously in the same way. The solenoid valve 78 is biased towards its middle position, the closed position, when not electrically influenced. When the circuit is closed, in which the switch 106, the relay 1 10, the main relay 63, and one of the solenoids of the valve 78 are connected, the valve 78 takes up the position in which its left square is connected instead of its middle square. The pressure chamber 74 of the jack 16 is now supplied with hydraulic fluid through the conduit 87, 86 and the pressure chamber 73 drains through the conduit 66a and, as a result, the jack starts extending. All oil supplied to the jack 16 must pass the meter 94, and when the counter 102 reaches the value to which it has been pre-set, the counter switches the switch 106 into off-position which causes the relay 110 to take up off-position as well. As a result, the valve 78 returns to its middle position, the closed position, and the jack 16 stops extending.

The jack l6 retracts when the right square of the valve 78 is connected so that the pressure chamber 73 of the jack 16 is supplied with hydraulic fluid through the conduit 85, 87 and the pressure chamber 74 drains through the conduit 86, 91. The valve 78 moves to the left, i.e. connects its right square, when a second solenoid indicated at the right part of the valve is energized by means of a non-illustrated circuit.

Steering of the machine is effected very precisely by means of the four advance jacks 13-16 because the front frame 11 and the rear frame 12 are interconnected only by the advance jacks 13-16 which have independently pre-set strokes.

Horizontally, the front frame 11 is guided during advance by the jacks 27, 28. The vertically arranged jacks 31-34 may be used for guiding the front frame 1 l vertically during advance, but, since there is always mud on the floor, the steering will be more precise when, during advance of the front frame 11, the front frame is held vertically in position mainly by the advance jacks. The clutches 111, 112 are used for this purpose to connect mechanically the meter 91 to the meter 92 and the meter 93 to the meter 94 during an advance of the front frame 11. During the very last portion of an advance, e.g. during the last 5 10 percent of an advance, the clutches 111, 112 are usually disengaged so as to permit all the advance jacks to stop independently of each other.

A machine with this combined steering and advancing system as described is normally fully automatized. The operator only presets the counters 99-102 to values corresponding to a wanted path and start the machine, and the machine will cut and advance in sequence. The machine moves in a constant rectilinear or curved path until the values of the counters 99-102 are changed. Normally, the operator therefore only needs to check the direction and, when necessary, adjust the counters.

It is to be understood that the described embodiment of the invention is only an example and that the invention may be varied in many ways within the scope of the claims.

What I claim is:

1. In a tunneling machine, a frame structure having a front and a rear portion, a cutting device mounted on said front frame portion adapted to swing about a transverse axis, means for bracing said front frame portion in the tunnel, means for bracing said rear frame portion in the tunnel, first and second hydraulic fluid actuated jack means for moving one of the frame portions in non-braced position longitudinally of the tunnel relative to the other frame portion, said first jack means being connected between the left hand sides of said frame portions and said second jack means being connected between the right hand sides of said frame portions, first supply conduit means for supplying fluid to said first jack means, second supply conduit means for supplying fluid to said second jack means, first valve means in said first supply conduit means, second valve means in said second supply conduit means, means for measuring the fluid supplied to said first jack means and actuating said first valve means into closed position when a predetermined volume has been supplied to the first jack means so as to limit an extension motion of the first jack means, and means for measuring the fluid supplied to said second jack means and actuating said second valve means into closed position when a predetermined volume has been supplied to the second jack means so as to limit an extension motion of the second jack means.

2. A tunneling machine as claimed in claim 1 in which: said first and second valve means are electrically controlled valve means; said means for measuring the fluid supplied to said first jack means and actuating said first valve means into closed position includes a rotary fluid motor connected in said first supply conduit means, a first counter driven by said motor, and a first electric switch connected in an electric circuit for actuating said first valve means, said counter being arranged with means to actuate said switch into a position for urging said first valve means into a closed position when said fluid motor has reached a pre-set number of revolutions; and said means for measuring the fluid supplied to said second jack means and actuating said second valve means into closed position includes a second rotary fluid motor connected in said second supply conduit means, a second counter driven by said second motor, and a second electric switch connected in a circuit for actuating said second valve means, said second counter being arranged with means to actuate said second switch into a position for urging said second valve means into a closed position when said second fluid motor has reached a pre-set number of revolutions.

3. A tunneling machine as claimed in claim 1 in which two cutting devices in the forms of frames are mounted for swinging about two spaced parallel vertical axes, and each of said two swingable frames is provided with a plurality of circular cutter heads which are rotated to cut tangentially as the frames are being swmg.

4. A tunneling machine as claimed in claim 1 in which said means for bracing said rear frame portion in the tunnel comprises at least three tunnel wall engaging shoes and at least one power jack operable to move one of said shoes of the rear frame portion to grip the wall for bracing the rear frame portion in the tunnel.

5. In a tunneling machine, a frame structure having a front portion and a rear portion, a cutting device mounted on said front frame portion adapted to swing about a transverse axis, means for bracing said front frame portion between two opposed walls of the tunnel, means for bracing said rear frame portion between two opposed walls of the tunnel, a first jack connecting the bottom parts of the left hand sides of said frame por tions, a second jack connecting the top parts of the left hand sides of said frame portions, a third jack connecting the bottom parts of the right hand sides of said frame portions, a fourth jack connecting the top parts of the right hand sides of said frame portions, a first supply conduit for supplying fluid to said first jack so as to effect extension thereof, a second supply conduit for supplying fluid to said second jack so as to effect exten sion thereof, a third supply conduit for supply fluid to said third jack so as to effect extension thereof, a fourth supply conduit for supplying fluid to said fourth jack so as to effect extension thereof, a first electrically controlled valve in said first supply conduit, a second electrically controlled valve in said second supply conduit, a third electrically controlled valve in said third supply conduit, a forth electrically controlled valve in said fourth supply conduit, a first rotary fluid motor in said first supply conduit, a second rotary fluid motor in said second supply conduit, a third rotary fluid motor in said third supply conduit, a fourth rotary fluid motor in said fourth conduit, a first counter driven by said first motor, a second counter driven by said second motor, a third counter driven by said third motor, a fourth counter driven by said fourth motor, a first electric switch connected in an electric circuit for actuating said first valve, a second electric switch connected in an electric circuit for actuating said second valve, a third electric switch connected in an electric circuit for actuating said third valve, and a fourth electric switch connected in an electric circuit for actuating said fourth valve, said first counter being arranged with means to actuate said first switch into a position for urging said first valve into a closed position when said first fluid motor has reached a pre-set number of revolutions, said second counter being arranged with means to actuate said second switch into a position for urging said second valve into a closed position when said second fluid motor has reached a pre-set number of revolutions, said third counter being arranged with means to actuate said third switch into a position for urging said third valve into a closed position when said third fluid motor has reached a pre-set number of revolutions, and said fourth counter being arranged with means to actuate said fourth switch into a position for urging said fourth valve into a closed position when said fourth fluid motor has reached a pre-set number of revolutions.

6. A tunneling machine as claimed in claim 5 in which said first and second motors are connected by a clutch so as to effect conjoined rotation of these motors, and in which said third and fourth motors are relesably connected by a clutch so as to effect conjoined rotation of these motors.

7. A tunneling machine as claimed in claim 5 in which said jacks are double acting jacks.

8. In a tunneling machine, a frame structure having a front portion and a rear portion, a pair of frames mounted on said front frame portion for swinging about two parallel but spaced vertical axes, each of said swingable frames being provided with a plurality of circular rotatable cutter heads adapted to cut tangentially during the swinging action of the frames, motor means for swinging said frames, first hydraulic fluid actuated jack means for bracing said front frame portion in the tunnel, first valve means connected to control said first jack means, second hydraulic fluid actuated jack means for bracing said rear frame portion in the tunnel, second valve means connected to control said second jack means, third and fourth hydraulic fluid actuated jack means for advancing one of the frame portions in non-braced position longitudinally of the tunnel relative to the other frame portion, said third jack means being connected between the left hand sides of said frame portions and said fourth jack means being connected between the right hand sides of said frame portions, first supply conduit means for supplying fluid to said third jack means, second supply conduit means for supplying fluid to said fourth jack means, third valve means in said first supply conduit means, fourth valve means in said second supply conduit means, means for measuring the fluid supplied to said third jack means and actuating said third valve means into closed position when a predetermined volume has been supplied to the third jack means so as to limit an extension motion of the third jack means, means for measuring the fluid supplied to said fourth jack means and actuating said fourth valve means into closed position when a predetermined volume has been supplied to the fourth jack means so as to limit an extension motion of the fourth jack means, means for actuating said valves and said motor means in a predetermined sequence whereby sequentially, the rear frame is braced in the tunnel but the front frame released, the third and fourth jacks are extended a step until they are arrested as a result of action of said means for measuring the fluid supplied to the third and fourth jacks, the front frame is braced, the swingable frames are reciprocated to perform swing cuts, the advance of the front frame and swing of the frames being repeated at least once and, then, the rear frame is released, advanced, and again braced, and advancing of the front frame portion and swinging of the frames are effected repeatedly. 

1. In a tunneling machine, a frame structure having a front and a rear portion, a cutting device mounted on said front frame portion adapted to swing about a transverse axis, means for bracing said front frame portion in the tunnel, means for bracing said rear frame portion in the tunnel, first and second hydraulic fluid actuated jack means for moving one of the frame portions in non-braced position longitudinally of the tunnel relative to the other frame portion, said first jack means being connected between the left hand sides of said frame portions and said second jack means being connected between the right hand sides of said frame portions, first supply conduit means for supplying fluid to said first jack means, second supply conduit means for supplying fluid to said second jack means, first valve means in said first supply conduit means, second valve means in said second supply conduit means, means for measuring the fluid supplied to said first jack means and actuating said first valve means into closed position when a predetermined volume has been supplied to the first jack means so as to limit an extension motion of the first jack means, and means for measuring the fluid supplied to said second jack means and actuating said second valve means into closed position when a predetermined volume has been supplied to the second jack means so as to limit an extension motion of the second jack means.
 2. A tunneling machine as claimed in claim 1 in which: said first and second valve means are electrically controlled valve means; said means for measuring the fluid supplied to said first jack means and actuating said first valve means into closed position includes a rotary fluid motor connected in said first supply conduit means, a first counter driven by said motor, and a first electric switch connected in an electric circuit for actuating said first valve means, said counter being arranged with means to actuate said switch into a position for urging said first valve means into a closed position when said fluid motor has reached a pre-set number of revolutions; and said means for measuring the fluid supplied to said second jack means and actuating said second valve means into closed position includes a second rotary fluid motor connected in said second supply conduit means, a second counter driven by said second motor, and a second electric switch connected in a circuit for actuating said second valve means, said second counter being arranged with means to actuate said second switch into a position for urging said second valve means into a closed position when said second fluid motor has reached a pre-set number of revolutions.
 3. A tunneling machine as claimed in claim 1 in which two cutting devices in the forms of frames are mounted for swinging about two spaced parallel vertical axes, and each of said two swingable frames is provided with a plurality of circular cutter heads which are rotated to cut tangentially as the frames are being swing.
 4. A tunneling machine as claimed in claim 1 in which said means for bracing said rear frame portion in the tunnel comprises at least three tunnel wall engaging shoes and at least one power jack operable to move one of said shoes of the rear frame portion to grip the wall for bracing the rear frame portion in the tunnel.
 5. In a tunneling machine, a frame structure having a front portion and a rear portion, a cutting device mounted on said front frame portion adapted to swing about a transverse axis, means for bracing said front frame portion between two opposed walls of the tunnel, means for bracing said rear frame portion between two opposed walls of the tunnel, a first jack connecting the bottom parts of the left hand sides of said frame portions, a second jack connecting the top parts of the left hand sides of said frame portions, a third jack connecting the bottom parts of the right hand sides of said frame portions, a fourth jack connecting the top parts of the right hand sides of said frame portions, a first supply conduit for supplying fluid to said first jack so as to effect extension thereof, a second supply conduit for supplying fluid to said second jack so as to effect extension thereof, a third supply conduit for supply fluid to said third jack so as to effect extension thereof, a fourth supply conduit for supplying fluid to said fourth jack so as to effect extension thereof, a first electrically controlled valve in said first supply conduit, a second electrically controlled valve in said second supply conduit, a third electrically controlled valve in said third supply conduit, a forth electrically controlled valve in said fourth supply conduit, a first rotary fluid motor in said first supply conduit, a second rotary fluid motor in said second supply conduit, a third rotary fluid motor in said third supply conduit, a fourth rotary fluid motor in said fourth conduit, a first counter driven by said first motor, a second counter driven by said second motor, a third counter driven by said third motor, a fourth counter driven by said fourth motor, a first electric switch connected in an electric circuit for actuating said first valve, a second electric switch connected in an electric circuit for actuating said second valve, a third electric switch connected in an electric circuit for actuating said third valve, and a fourth electric switch connected in an electric circuit for actuating said fourth valve, said first counter being arranged with means to actuate said first switch into a position for urging said first valve into a closed position when said first fluid motor has reached a pre-set number of revolutions, said second counter being arranged with means to actuate said second switch into a position for urging said second valve into a closed position when said second fluid motor has reached a pre-set number of revolutions, said third counter being arranged with means to actuate said third switch into a position for urging said third valve into a closed position when said third fluid motor has reached a pre-set number of revolutions, and said fourth counter being arranged with means to actuate said fourth switch into a position for urging said fourth valve into a closed position when said fourth fluid motor has reached a pre-set number of revolutions.
 6. A tunneling machine as claimed in claim 5 in which said first and second motors are connected by a clutch so as to effect conjoined rotation of these motors, and in which said third and fourth motors are relesably connected by a clutch so as to effect conjoined rotation of these motors.
 7. A tunneling machIne as claimed in claim 5 in which said jacks are double acting jacks.
 8. In a tunneling machine, a frame structure having a front portion and a rear portion, a pair of frames mounted on said front frame portion for swinging about two parallel but spaced vertical axes, each of said swingable frames being provided with a plurality of circular rotatable cutter heads adapted to cut tangentially during the swinging action of the frames, motor means for swinging said frames, first hydraulic fluid actuated jack means for bracing said front frame portion in the tunnel, first valve means connected to control said first jack means, second hydraulic fluid actuated jack means for bracing said rear frame portion in the tunnel, second valve means connected to control said second jack means, third and fourth hydraulic fluid actuated jack means for advancing one of the frame portions in non-braced position longitudinally of the tunnel relative to the other frame portion, said third jack means being connected between the left hand sides of said frame portions and said fourth jack means being connected between the right hand sides of said frame portions, first supply conduit means for supplying fluid to said third jack means, second supply conduit means for supplying fluid to said fourth jack means, third valve means in said first supply conduit means, fourth valve means in said second supply conduit means, means for measuring the fluid supplied to said third jack means and actuating said third valve means into closed position when a predetermined volume has been supplied to the third jack means so as to limit an extension motion of the third jack means, means for measuring the fluid supplied to said fourth jack means and actuating said fourth valve means into closed position when a predetermined volume has been supplied to the fourth jack means so as to limit an extension motion of the fourth jack means, means for actuating said valves and said motor means in a predetermined sequence whereby sequentially, the rear frame is braced in the tunnel but the front frame released, the third and fourth jacks are extended a step until they are arrested as a result of action of said means for measuring the fluid supplied to the third and fourth jacks, the front frame is braced, the swingable frames are reciprocated to perform swing cuts, the advance of the front frame and swing of the frames being repeated at least once and, then, the rear frame is released, advanced, and again braced, and advancing of the front frame portion and swinging of the frames are effected repeatedly. 